We "hear" all the time that high phosphate levels are the cause of everything bad in your pool....but that's usually from pool store people who don't really know what else to do except sell you some phosphate remover.
If you are having problems keeping chlorine in the pool, odds are that you either have an algae bloom trying to happen, or that your stabilizer isn't high enough. Where do you live, and how much sun does your pool get in a day?
Also, have you checked to see if you're losing that chlorine during the day or at night? If you test at night and again in the morning before the sun is on the pool, and you don't lose any chlorine, then you're probably losing it to sunlight and need to bump your stabilizer up a little. (BTW, I've never seen a tester that can determine CYA levels lower than 30 ppm--where did your result come from?) If you do lost chlorine during that overnight test, then you need to elevate your chlorine levels to "shock" level (see the link in my sig to the "best guess" chart to see what that level is) and hold it there until you're no longer losing chlorine during the night time.
I seriously doubt phosphates are the problem.
Janet
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